The primary objective is to show whether fast neutron therapy is superior to best current treatment methods for locally advanced cancer. In addition to a continuation of the clinical trial in human cancer, research in physics, radiobiology, and animal tumor therapy will be carried out in order to 1) better define the radiation dose delivered, 2) evaluate acute and late effects on normal tissues, 3) study dose fractionation, and 4) compare the physical and radiobiological characteristics of the TAMVEC beams with those of other neutron facilities (MANTA, UW, and Hammersmith). Fractionation studies will be emphasized, since a preliminary interpretation of radiobiology and clinical results have indicated that the increased incidence of radiation sequelae (fibrosis and soft tissue necrosis) may be due to the large dose twice weekly fractionation schedules employed. The Phase I clinical trial of fast neutron therapy began in October 1972. National cooperative clinical trials (TAMU-MDAH, MANTA, UW), are planned for May 1975. These will consist of non-randomized studies for tumors where the results with conventional treatment methods are uniformly poor and randomized studies for tumors where conventional radiotherapy and/or surgery have shown limited effectiveness. The advantages of this study are the high dose rate, variable and high energies available with the TAMVEC cyclotron, which make this beam suitable for treating deep seated tumors, and the large patient load and clinical experience at MDAH. BIBLIOGRAPHIC REFERENCES: Hogstrom, K.R., and Smith, A.R., Almond, P.R., Otte, V.A., and Smathers, J.B.: Computer dosimetry for flattened and wedged fast-neutron beams. Medical Physics 3:26-30, Jan/Feb l976. Smathers, J.B., Otte, V.A., Smith, A.R., and Almond, P.R.: Fast neutron dose rate vs energy for the d ion Be reaction--a reanalysis. Medical Physics 3:45-47, Jan/Feb 1976.